The present invention relates generally to ink jet printing systems. More particularly, the present invention relates to a drop-on-demand printing system that reduces the effect of aerodynamic induced errors during printing.
An ink jet printer produces a printed image by printing a pattern of individual dots (or pixels) at specific defined locations of an array. These dot locations, which are conveniently visualized as being small dots in a rectilinear array, are defined by the pattern being printed. The printing operation, therefore, can be pictured as the filling of a pattern of dot locations with dots of ink. Ink jet printers are described in detail in U.S. Pat. No. 6,270,201, incorporated herein by reference.
Ink jet printers print dots by ejecting a small volume of ink onto the print medium. These small ink drops are positioned on the print medium by a moving carriage that supports a printhead cartridge containing ink-drop generators. The carriage traverses over the print medium surface and positions the printhead cartridge depending on the pattern being printed. An ink supply, such as an ink reservoir, supplies ink to the drop generators. The drop generators are controlled by a microprocessor or other controller and eject ink drops at appropriate times upon command by the microprocessor. The timing of ink drop ejections typically corresponds to the pixel pattern of the image being printed.
In general, the drop generators eject ink drops through a nozzle or an orifice by rapidly heating a small volume of ink located within a vaporization or firing chamber. The vaporization of the ink drops typically is accomplished using an electric heater, such as a small thin-film (or firing) resistor. Ejection of an ink drop is achieved by passing an electric current through a selected firing resistor to superheat a thin layer of ink located within a selected firing chamber. This superheating causes an explosive vaporization of the thin layer of ink and an ink drop ejection through an associated nozzle of the printhead.
The resolution of an ink jet printer is directly related to the size and number of ink drops printed on a print medium. For example, for a given area a small number of large ink drops produces a relatively low-resolution printed image while a large number of small ink drops generally produces a higher-resolution printed image. The quality and resolution of printed images that a printer is capable of producing are often compared to photographs, and xe2x80x9cphotographic-qualityxe2x80x9d resolution means that the resolution approaches that of a photograph.
There is a continually increasing demand for low-cost ink jet printers that are capable of producing xe2x80x9cphotographic-qualityxe2x80x9d images. Achieving this high resolution while keeping costs low requires a careful balance between the architecture of the printhead (such as the architecture of the firing chamber, the firing resistor and the firing frequency) and the composition of liquid ink. Typically, a change in the printhead architecture or in the ink composition to solve one problem may create other problems. Thus, in order to produce an inexpensive ink jet printer capable of photographic-quality resolution, several factors in the printhead architecture and ink composition should be taken into account.
Additionally, six-color ink printing systems have been developed in which certain light-dye inks are used only for lower speed, higher quality printing, while other dark dye inks are used either solely for higher speed, lower quality printing or, when necessary, both higher and lower speed printing.
As the size of the individual ink drops is decreased, however, a number of difficulties arise. The sizes of the ink drops that are often used to produce high quality photographic images are often in a size range that can be adversely affected by nearby air disturbances. Standard inkjet printing systems include a plurality of rows of nozzles, with each row of nozzles coupled to a reservoir of ink of a different color. As the rows of nozzles are placed closer together, however, the motion of ink drops traveling through the air from the nozzles to the printing surface affects the direction of ink drops released from adjacent rows of nozzles, causing them to miss their intended target on the printing surface by some amount of error. Thus, the air disturbance caused by the ink drops results in a reduction of quality of the images being produced on the printing surface.
This problem is exacerbated as inkjet electronics and fluidic architectures are reduced in size in order to lower costs. As components such as smaller, lower-cost silicon chips are used, nozzle rows are positioned closer together and the amount of air disturbance that occurs between the rows of nozzles and the printing surface increases, further reducing the print quality.
There have been a number of potential solutions to the problem described above, but each has its own drawbacks. For example, reducing the printing speed can reduce the amount of air disturbance. The problem with such an approach, however, is that the amount of time for completing a print job is increased. An alternative approach has been to increase the number of multiple print passes in order to hide the defects caused by the aerodynamic disturbances. Increasing the number of multiple passes, however, also increases the amount of time for printing.
The present invention provides an effective system for reducing the problems associated with aerodynamic disturbances caused by ink drops as they are deposited on a printing surface.
The present invention comprises a multiple ink jet printing system including a plurality of rows of dark dye nozzles and light dye nozzles (also referred to as dark dye loads nozzles and light dye loads nozzles, respectively). Each row of dark dye nozzles is coupled to a supply of dark dye ink, and each row of light dye nozzles is coupled to a supply of light dye ink. Each of the rows of dark dye nozzles and light dye nozzles are arranged substantially parallel to each other, and at least one row of dark dye nozzles is separated from the next row of dark dye nozzles by at least one row of light dye nozzles.
The present invention also comprises a multiple ink jet printing system, which in some embodiments is a six ink jet printing system, a seven ink jet printing system, or an eight ink jet printing system. It includes a plurality of rows of dark dye nozzles coupled to supplies of ink of different colors, such as yellow, magenta, and cyan. It includes a plurality of rows of light dye nozzles are coupled to supplies of ink of different colors, such as yellow, black, magenta, and cyan. It includes one or more rows of black dye nozzles coupled to a supply of black ink. In some embodiments of the invention, these black dye nozzles are located at one end of the plurality of nozzle columns. Light yellow and/or light black nozzle columns are absent from some embodiments of the invention. Each of the rows of dark dye nozzles, light dye nozzles, and black dye nozzles are arranged substantially parallel to each other, and at least one row of dark dye nozzles is separated from the next row of dark dye nozzles by a row of light dye nozzles. In some embodiments, dark and light dye rows of nozzles alternate. In an alternative arrangement, the dark and light dye rows of nozzles alternate, but a yellow dark dye nozzle is positioned adjacent an adjoining dark dye nozzle of some other color, or a yellow dark dye nozzle is positioned adjacent the one or more rows of black dye nozzles.
The present invention also comprises a drop-on-demand printing system having a plurality of nozzle columns including a plurality of columns of dark dye nozzles, with each column of dark dye nozzles coupled to a source of dark dye ink. Each of a plurality of columns of light dye nozzles is coupled to a source of light dye ink, and a column of black dye nozzles is coupled to a source of black dye ink. The column of black dye nozzles is located at one end of the plurality of nozzle columns, and each of the columns of dark dye nozzles and light dye nozzles are arranged substantially parallel to each other. At least one column of dark dye nozzles is separated from the next column of dark dye nozzles by a column of light dye nozzles. This embodiment of the invention also includes the variations listed in the preceding paragraph.